The airbag ECU is a critical safety-system component that continuously monitors the crash accelerometers (integrated into the ECU itself rather than mounted separately) and triggers airbag deployment in a collision. The ECU changed specification twice across production. Up to VIN 5D639630, MGF and MG TF cars were fitted with one of two ECU specifications: a driver-airbag-only version on single-airbag cars, and a driver-and-passenger version on dual-airbag cars. From VIN 5D639631 onwards, MG TF cars used a universal ECU that is configured at fitting using Rover Testbook, this requires a specialist dealer-level diagnostic tool rather than a generic OBD scanner, so the post-MY2005 universal ECU typically needs to be fitted by a workshop with the correct equipment.
Airbag ECU mounting bracket and securing screws also changed: at AD021170 (screw change) and at 5D639631 (bracket change). An airbag warning light that remains illuminated after ignition-on indicates a fault that must be investigated, the airbags may not deploy in a collision if the system has a stored fault.
Airbags, Handed Passenger Airbag by Interior Colour
The driver's airbag module is a single specification across the range, mounted in the steering wheel centre and retained by two bolts. The passenger airbag module, mounted in the dashboard, is a different matter: it is catalogued in five interior colour variants, Ash Grey, Walnut (MGF from XD511059 onwards), Grenadine Red, Light Smokestone (MG TF), and Light Tan, because the airbag cover is part of the visible dashboard trim. Ordering a passenger airbag requires knowing the interior colour specification, which for special editions and late trim specifications should be confirmed against the original build sheet rather than eyeballed. Passenger airbag mounting uses M8 Kleerlok bolts, M6 bolts, and M5 nuts as separate catalogued items.
Alarm ECU and Remote, 433MHz and 315MHz Are Not Interchangeable
The alarm ECU and its matching remote transmitter are radio-paired and must be ordered to the correct frequency. UK and most European markets use 433MHz; Japan, Australia, and some other markets use 315MHz. Do not assume the car uses 433MHz without checking: the label on the remote is typically worn off by years of handling, but the label on the ECU body is usually still legible since the ECU is mounted out of harm's way. The alarm ECU itself changed specification for MG TF from VIN 4D620549 onwards, requiring a different ECU and a different matched remote; MGF and pre-4D620548 MG TF cars use an earlier ECU and remote pairing.
Four ECU/remote combinations are catalogued in total across the 433MHz/315MHz and pre/post-4D620549 matrix. A dedicated 2-button remote repair kit is catalogued for remotes where the button rubber has perished.
Replacement key fob batteries are a simple owner-level renewal item, the correct battery is catalogued individually for all variants.
Immobiliser Transmitter
The immobiliser transmitter is a separate 433MHz fob, distinct from the alarm remote, that communicates with the immobiliser function integrated into the MEMS engine management ECU. On MY2000 and later cars with MEMS 3, the immobiliser ECU is paired to the engine ECU and the key transponder, and replacement transmitters require programming to the specific car, a specialist operation rather than an over-the-counter swap.
Door and Bonnet Contact Switches
Four identical contact switches are fitted to the MGF and MG TF, at each door and at the bonnet. These are dual-function items: they trigger the alarm system when the car is armed, and they control courtesy light operation at all times. A faulty switch can therefore present as an alarm false-triggering, an alarm that fails to arm, or simply a courtesy light that stays on or stays off, the same physical switch serves both systems. Switches are retained by small self-tapping screws catalogued individually.